Panoramic images are used to provide immersive “surround” views of scenes, up to 360° in extent. Digital panoramic images can be archived on Internet servers, for access by remote clients. Panoramic images are typically texture mapped into a suitable surface geometry, such as a cylindrical or a spherical geometry. Texture mapping generates a “warped” look to the panorama, and usually converts straight lines into bowed curves.
Client viewer software enables users to interactively view panoramic images by navigating through the panorama. Specifically, for a prescribed view window on a client computer video display, client viewer software converts a selected portion of the panoramic image at a selected level of magnification from cylindrical or other surface geometry to rectilinear geometry, which is appropriate for typical perspective viewing. The converted portion of the panoramic image is displayed in the view window.
A user interface enables a user to dynamically change the selected portion of the panoramic image being viewed. Rapid display of the dynamically changing selected portion gives the viewer a sensation of moving through the panorama, and an experience of being immersed within the surrounding scene. Typically a user interface enables a user to select portions of the panoramic image for display by indicating shifts and changes in magnification of a current portion of the panoramic image, rather than by selecting a new portion without reference to the current portion. Typically the user interface provides for shifting the selected portion up, down, left, right, or other directions, and for reducing or enlarging the current magnification factor, by zooming in and out. Such a user interface can include, for example, keyboard buttons or mouse controls and movements.
Panoramic content creation is typically carried out by a photographer who captures multiple photos of a scene, as he rotates his camera around in a circle. For typical camera lenses such as a 35 mm video camera lens, the photos acquired are characterized by a rectilinear geometry. That is, there exists a linear correspondence between distances in the photo and distances in the scene. Each such photo represents a portion of the scene. The photos are digitized by a digital scanner or, in a case where the photographer uses a digital camera, the photos are digitized by hardware within the camera.
The digital photos are then downloaded to a computer, and a “stitching” application is run to combine the digital photos into a single panoramic image. An example of such a stitching application is assignee's PhotoVista® software.
The photographer can eliminate the combining step by capturing a large portion of a scene by using a wide angle lens, or a hemispherical lens such as the Portal lens system of Be Here Corporation, or a parabolic lens such as the ParaShot™ attachment of CycloVision Technologies, Inc., the latter two of which capture a 360° image in one exposure.
When a photographer creates a panoramic image by combining multiple photos, typically he must be careful to ensure that adjacent fields of view are appropriately aligned as he rotates the camera. When rotating the camera in a horizontal plane, such alignment involves providing for horizontal overlap between adjacent photos, and minimizing vertical displacements outside of the horizontal plane of rotation. Similarly, when rotating the camera in a vertical plane, such alignment involves providing for vertical overlap between adjacent photos, and minimizing horizontal displacements outside of the vertical plane of rotation.
In the ensuing discussion, for the sake of conciseness and simplicity of explanation, panoramas in a horizontal plane of rotation are described, it being understood that the present invention is not limited to panoramas in a horizontal plane of rotation.
When rotating the camera freely in his hand, it is difficult for a photographer to accurately align adjacent fields of view. A reliable way for a photographer to align adjacent fields of view is to mount his camera on a tripod, using a tripod bracket that has equi-spaced notches for rotating the camera in increments of a fixed angle. An example of such a bracket is the Kaidan KiWi™ tripod head. Typically such tripod brackets include one or more spirit levels, so that a photographer can adjust the tripod to keep the axis of rotation of the camera vertically disposed.
Use of a computer for combining acquired photos to produce a panoramic image has several disadvantages. One disadvantage is that the photographer needs to take a computer with him in the field. Otherwise, he cannot create and view the panoramic image while in the field. There are problems associated with both of these situations.
The first option of taking a computer in the field can be difficult, because often a photographer has to hike through un-trodden ground in order to find “the perfect scene.” Carrying both a camera and a computer along with his food and gear can be burdensome on the photographer.
Even when the photographer does take a computer with him in the field, he may have to move the camera from its axis of rotation in order to download the photos acquired thereby. As soon as a camera is moved from its axis of rotation, typically the only way to re-generate a panoramic image is to recapture at a new axis of rotation all of the individual photos included in the panorama. For example, if one of sixteen frames of a scene comes out bad, the photographer can correct the problem and recapture such frame as long as the camera has not been moved from its axis of rotation. However, once the camera has been moved from its axis of rotation, a single frame cannot normally be accurately aligned within previously acquired adjacent frames. Thus, even when using a notched tripod bracket, the photographer will normally have to recapture all of the photos included in the panoramic image.
The second option of not creating the panoramic image in the field is problematic, because the photographer cannot see the quality of his panoramic image while in the field. If he subsequently discovers problems with the panoramic image, it may very well be hard, if not impossible, to return to the scene in the same favorable weather and other conditions.